I am trying to populate drop boxes - vb.net

Question

Here is what I have so far to populate a couple drop down boxes in visual basic.
I may need global variables but I am not sure how to do that. I have been told to use Dim and the variable names of the drop boxes but I keep getting errors saying they are already friends within the form.
*This is a homework assignment, however I am not asking you to do the assignment but simply asking help with the problem I am having within the drop boxes. I don't expect you wonderful people to earn my grades for me! Thank you for any help!
Public Class Form1
'// Mortgage Calculator Assignment 1.
'// Can calculate payments on a given loan at a given rate for a given term.
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
'// Inputs rate starting at 3.25% through 6.75% at steps of 0.25% into the drop down box.
Private Sub cbRate_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbRate.SelectedIndexChanged
For i As Decimal = 3.25 To 6.75 Step 0.25
cbRate.Items.Add(i & "%")
Next
End Sub
'// Inputs term in years from 10 through 40 at steps of 5 year intervals into the drop down box.
Private Sub cbTerm_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbTerm.SelectedIndexChanged
For i As Integer = 10 To 40 Step 5
cbTerm.Items.Add(i)
Next
End Sub
End Class

Answer 1

You do not need global variables.
Try just populating the combo boxes in the form load:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'// Inputs rate starting at 3.25% through 6.75% at steps of 0.25%
' into the drop down
For i As Decimal = 3.25 To 6.75 Step 0.25
cbRate.Items.Add(i & "%")
Next
'// Inputs term in years from 10 through 40 at steps of 5 year intervals
' into the drop down box.
For i As Integer = 10 To 40 Step 5
cbTerm.Items.Add(i)
Next
End Sub
Edit: the combo boxes were declared (probably) for you when you added them to the form in the designer.